When I click on the Settings - Publishing options, I don't even have the option to check availability or purchase a domain name. Where is the "Buy a domain" display?Right now, it appears that "Buy a domain" was sacrificed, so that the general custom domain publishing feature could be restored more promptly (though not promptly enough, for many blog owners). There are several tasks that must be completed by "Buy a domain", which are complex - and the necessary coding simply could not be completed by Tuesday of this week. I saw one message of hope.
We will be restoring the ability to purchase a custom domain from Blogger soon.We'll simply have to have faith, that they are working on this feature as we lament its current absence - and that its absence is brief..
In the mean time, some wanta be domain owners have found a domain purchase wizard provided by Google Apps - though that's not "Buy a domain". Google Apps has two different wizards providing domain purchase options, each with a widely different address and Top Level Domain menus.
(Update 2012/10/09): "Buy a domain for your blog" is once again part of the Publishing wizard.